1. Field of the Invention
This invention relates to an automatic feed device for use in connection with a numerically controlled machine tool having an automatic tool exchanger, known as a machining center, which is automatically arranged on the main shaft of a machine tool so as to permit automatic facing with the aid of a cutting tool, by means of numerical data recorded and stored on magnetic tapes and the like, thereby requiring no manual operation.
2. Description of the Prior Art
In a prior general-purpose machine tool such as a milling machine and the like, a body is arranged at the lower end portion of a shank mounted to the main shaft of the machine tool. Further, a cutting tool support mechanism is free to slide on the lower end surface of the body through dovetail slots extending in a direction normal to the axis of the main shaft. Upon rotation of the main shaft, the cutting tool support mechanism is moved in a transverse direction, a direction normal to the axis of the main shaft, by automatic feed or return means, to thereby effect facing by the use of a cutting tool. However, such means requires manual operation by the operator.
It should be mentioned that it is inefficient for the operator to stop rotation of the main shaft during automatic operation of a machining center and to manually operate the machine tool, and that automatic operation of the machine tool is thus impossible. It should also be mentioned that the cutting tool support mechanism is moved by rotation of the main shaft. However, since such movement of the cutting tool support mechanism provides an output for stopping feeding of the cutting tool, no output is provided once the cutting tool support mechanism is stopped. It is considered, therefore, that rapid returning and feeding of the cutting tool support mechanism is not automatically effected.
In the course of automatic operation of the machining center, the number of rotation of the main shaft per minutes as well as the time of rotation thereof are determined under a numerical control system. There may thus be errors when the rotation of the main shaft is started or stopped. Also, when the tool is exchanged, the main shaft needs to be rotated so as to stop the cutting tool support mechanism in a fixed position. When rapid returning of the cutting tool support mechanism is complete, the cutting tool support mechanism must be stopped in a fixed position independently of the rotation of the main shaft. Otherwise, a starting position from which the cutting tool is fed becomes unstable by reason of the foregoing. Also the movement of the cutting tool support mechanism provides an output for stopping rapid returning and feeding in the same manner as mentioned above. Thus, no output is provided if such rapid returning and feeding of the cutting tool support mechanism is stopped.